This disclosure relates generally to required navigation performance (RNP) procedures, and more particularly to methods, apparatus, and design systems for aircraft traffic control based on required navigation performance standards and metrics.
Performance-based aircraft applications include area navigation (RNAV) and required navigation performance (RNP) systems and metrics. These systems and metrics define certain performance levels, performance, functionality, and capability as agreed-upon standards. The aviation community has been broadly adopting RNAV and RNP. The FAA is implementing RNAV and RNP for operations conducted under instrument flight rules (IFR), but RNAV and RNP are not being required under visual flight rules (VFR).
“RNAV”, as used herein, refers to a method of navigation that enables aircraft to fly on any desired flight path within the coverage of referenced navigation aids (NAVAIDS), Global Positioning System (GPS) or within the limits of the capability of self-contained systems, or a combination of these capabilities. Routes and procedures using RNAV provide improved access and flexibility through point-to-point navigation and are not restricted to the location of ground-based NAVAIDS. The targeted level of safety is achieved via combined use of aircraft navigation accuracy, radar monitoring, automatic dependent surveillance (ADS) and/or additional separation buffers. Examples of systems used for RNAV operations today are flight management systems (FMS) and panel-mount IFR global positioning system (GPS).
“RNP,” as used herein, refers to operations with navigation containment and monitoring. An RNP system allows an aircraft navigation system to monitor its achieved navigation performance and to identify whether the operational requirement is not being met during an operation. RNP capability of an aircraft is a major component in determining the separation criteria to ensure that the target levels of safety are met. For example, when flying an RNP procedure an airplane must be qualified and capable of flying with an actual navigation precision equal to or greater than the required navigation performance prescribed by the procedure.
Aircraft using RNP procedures are required to turn or guide themselves accurately on a procedure. RNP procedures are now mandatory for certain difficult to navigate to, terrain challenged, airports, such as those in Tibet, in very high-altitude mountainous areas in South America, and some in Alaska. Certain of these airports have no straight-in approaches, but only approaches with mountainous terrain on both sides and therefore some turns are required in these approaches. RNP is well known for providing precision approaches in such areas. However, aircraft manufacturers and operators would like to use RNP to enable pilots to fly aircraft more efficiently when approaching other airports. For example, by merely applying the same approach, speed, and decent rate to every given aircraft, which is one current non-RNP approach, a pilot cannot operate an aircraft nearly as efficiently. Nevertheless, acceptance of RNP procedures is not being achieved at high congestion airports, because air traffic controllers (ATCs) cannot easily combine airplanes flying customized RNP approaches with air traffic unable to conduct a RNP approach. Since the ATCs primary concern is keeping two aircraft from being in the same location at the same time rather than the efficiency of the approach for any particular aircraft, the RNP procedures are not being accepted. As a result, many aircraft are not operating with peak efficiency due to constraints applied by ATCs.
While known RNP procedures could provide improved efficiency for aircraft capable of flying RNP approaches, they are not used by ATC since a faster aircraft could potentially overtake a slower aircraft flying in the same traffic pattern. Thus, current RNP approaches do not integrate well with the type of traffic patterns and separation requirements that local ATCs prefer, and the potential savings in fuel, operations and emissions are therefore not realized.
It would therefore be desirable to provide methods, apparatus, and design systems that achieve separation requirements for aircraft in a high volume terminal airspace situation as well as reduce the amount of workload on the air traffic control workforce to direct traffic safely to a runway end. A precision procedure that would meet with acceptance by local ATCs would also be desirable.